Mayson, Tanja Anick MSc, BSc, PT; Harris, Susan R. PhD, PT; Bachman, Catherine L. PhD, OT
Research has shown benefits of early identification of children with atypical or delayed development.1,2 Although results of early intervention are conflicting,2–5 identification, in conjunction with referral to appropriate services, can maximize developmental outcomes.1,6 Many discriminative motor tools compare children’s development to (1) a normative sample that is not ethnically diverse7 (or whose ethnic make up is not discussed),8 (2) a normative sample that represents some but not all of a country’s ethnic backgrounds,9 or (3) a normative sample consisting of children of diverse ethnic backgrounds that represent each ethnic origin in proportion to the actual population.10–12 Variations in gross motor development of children of different ethnic origins have been documented in the literature,13 including differences in motor development among children of different ethnic backgrounds living within countries such as Israel14 and the United States.15–20
Therefore, even if tests have been standardized on samples representative of ethnically diverse populations, they may not accurately represent the gross motor development of one specific ethnic group included in the normative sample, ie, if one ethnicity comprises a majority of a normative sample, the mean comparison data will be skewed toward their results.
For example, an ethnically diverse sample consisting of mostly European children will likely have a mean score closer to the mean of the European subgroup than to the means of subgroups of other ethnic origins. European children are therefore more likely to have a score that is closer to the normative sample mean than children of other ethnic origins. Children from other ethnic origins may have motor skill levels that are typical of their own ethnic origin yet may appear advanced or delayed when compared to the normative data, leading to incorrect conclusions regarding their development.
This review examines similarities and differences in neuromotor development among children of European and Asian origins, two well-represented ethnic groups in Canada21 and the United States. Knowledge gained through this review will foster better understanding of child development and help clarify whether the comparison scores used in discriminative tools and other norm-referenced measurement tools are appropriate.
CINAHL, EBM Databases, EMBASE, ERIC, MEDLINE, and PsychINFO databases were searched for articles related to motor development of children of European and Asian backgrounds. Subject headings and keywords included: motor development, motor skills, child development, psychomotor performance, ethnic groups, Asian continental ancestry group, Asians, culture, race, continental population groups, cross-cultural comparison, European continental ancestry group, ethnic groups, and ethnicity. Search terms relating to development were combined with “or” as were search terms relating to ethnicity. The results of the grouped searches for development and ethnicity were then combined with “and” to retrieve articles pertaining to the development of children of different ethnic backgrounds. Lastly, the search was limited to studies of individuals ages 0–18 years, where possible. No limits were set for year of publication.
Inclusion criteria were original research or secondary analysis of previous original results; studies that used gross motor, discriminative, standardized tests or motor milestone achievement in participants below the age of 18 years; and study participants of East Asian, South-East Asian, or European origin.
A review of article titles yielded 32 articles. After reviewing the articles’ abstracts, 11 articles met the inclusion criteria. A search of retrieved articles’ reference lists led to six additional articles that met criteria for this review. Of the articles retrieved, 16 included results of standardized tests and one reported on motor milestone achievement. Those reporting standardized test results used only four of the many available discriminative motor tools to compare similarities and differences in motor development of children of European and Asian descent living throughout the world: the Denver Developmental Screening Test22 (DDST) and its revised version, the Denver II Developmental Screening Test (Denver II),23 the Movement Assessment of Infants (MAI),7 the Bayley-II,10 and the Movement Assessment Battery for Children (MABC).11 Results based on using these four tools to assess children from different ethnic groups will be discussed, followed by a review of the motor milestone achievement study.
The Denver Developmental Screening Test
A simple, clinically relevant tool used to screen for and detect early signs of developmental delay in infants and preschool-aged children, the DDST22 examines four developmental areas: gross motor, fine motor-adaptive, language, and personal-social behavior. The DDST was standardized on a sample of 1000 “white,” “Spanish,” and “black” children younger than 6.5 years of age in Denver, Colorado.21 Ueda24,25 used the DDST to assess 615 children aged 16 days to six years, four months in Japan, comparing their scores to the DDST normative data. The Japanese children attained gross motor skills significantly later than their American peers. For items “lifts head in prone,” “head to 45 degrees in prone,” “head to 90 degrees in prone,” “chest up with arm support in prone,” “rolls over,” and “walks up steps,” the age at which 50% of Japanese children passed the item was more than three times later than their American peers, or 1.1 to 8.6 months later. For these same items, the age at which 90% of Japanese children passed them was at least 0.2 times later than their American peers, or 1.1 to 13.1 months later.
Williams26 administered the DDST to 6606 children between the ages of two weeks and six and a half years in the Philippines and found that children in Metro-Manila achieved two-thirds of the items significantly later than their American peers. These results prompted the author to create a slightly different and more appropriate test for screening children in the Philippines, the Metro Manila Developmental Screening Test, with its own normative data and its own criteria for “typical development” in this population.
Williams and Williams27 conducted a cross-cultural comparison of children by administering the DDST in Metro-Manila, Tokyo, Okinawa, and the Netherlands. Ages at which 50% of children passed each item were compared. Children from Metro-Manila were delayed in attainment of most items compared with their American and Dutch peers and were most similar in age of skill attainment to their peers in Okinawa and Tokyo.
Miller et al.28 used the DDST to assess a sample of 25 randomly selected Southeast Asian refugee children between 13 months and five years of age who were living in the United States. Although there were differences between these children and the Denver normative sample in three DDST dimensions (fine motor-adaptive, personal-social, and language), there were no differences in gross motor skills.
Others have reported results that do not show such consistent differences. Chen29 used the DDST to compare development of 126 Malaysian children from birth to six years of age to the DDST normative data. Although Malaysian children were slightly slower in their gross motor skills during the first year of life, they were more advanced than their American peers during their second year. Similarly, two other studies that examined the restandardization of the DDST for use with Chinese children found that when assessing 1041 children living in Shanghai30 and 6886 children ages one to 72 months,31 Chinese children ages one to 72 months were advanced in some gross motor skills while their American counterparts were more advanced in other gross motor skills.
Sriyaporn and colleagues32 used the DDST to assess 1442 children in Bangkok who were two weeks to six years of age. Although the Bangkok children had 25th percentile scores on gross motor skills similar to the Denver sample, they were more delayed at the 75th to 95th percentile for each test item.
The Denver II23 was created to address concerns that had arisen from the DDST. The revision included modification of 21 items and addition of 43 new items. The normative sample consisted of more than 2000 children living in Colorado who were “white,” “Hispanic,” or “black.”9 Even with creation of the revised version of the DDST, Lim and colleagues stated that a substantially different version of the Denver II needed to be created to accurately assess children in Singapore.33
The Movement Assessment of Infants
A standardized measure used to identify infants with neuromotor delays or disorders, the MAI7 evaluates four components of neuromotor behavior in the first year of life: muscle tone, primitive reflexes, automatic reactions, and volitional movements. The initial profiles created for this tool were based on a sample of 57 infants of which 55 were of European background.7
Toy and colleagues20 used the MAI to assess 30 six-month-old Asian-American infants born full-term without known risk factors, and compared their scores to those in Washington and Deitz’s34 study of predominantly European background age-peers. No between-group differences were found in muscle tone items. However, in the primitive reflexes section, Asian-American infants had less optimal scores than their peers of European background on two items—the Moro and Galant reflexes. Asian-American infants also had a greater frequency of less optimal scores in the automatic reactions section of the MAI than infants of European background in the earlier study,34 although overall scores for this section were similar between groups. Finally, significant differences between groups were identified in the volitional movement section. Asian-American infants received a much higher percentage of scores indicating “volitional movements appear immature for age.”
When Toy et al.20 used the six-month profile created from the Washington and Deitz’34 study, they noted that although 56% of the European background infants attained a risk score of zero, indicating no risk points, none of the Asian-American infants scored zero. Also, risk scores of ≥6 fall outside the range of scores for the Washington and Dietz34 study and, if used as a cut score for typical development, 40% (12 of 30) Asian-American infants would have been considered to be outside the typical range.
The Bayley Scales of Infant Development
The Bayley Scales of Infant Development (BSID) are standardized scales used to assist in identifying children with delays, to measure change in development, as well as assist in the planning and evaluation of intervention.35 The Bayley-II10 was created because of an identified need for revising the initial test’s norms.36 The revised edition includes two different scales, motor and mental, as well as an infant behavior record.10 The normative data for the second edition came from a sample of 1200 American children, with each age group stratified for gender, ethnicity, geographic region, and parental education. Ethnic backgrounds of children in the normative sample included “white,” African-American, and Hispanic, as well “other ethnic backgrounds” that included Asian-American, Native American, and Pacific Islanders in the same proportions of children aged one to 42 months in the U.S. population according to the 1988 U.S. census.10
Pomerleau and colleagues37 used the Bayley-II to assess motor development of young children adopted in Quebec, Canada. Children adopted from China and East Asia (Vietnam, Taiwan, Thailand, South Korea, Cambodia) were compared with children adopted from Russia. On arrival in Canada, Asian children had a higher psychomotor developmental index (PDI) than their Russian peers and, within the Asian subgroup East Asian children had greater PDI scores than their Chinese peers. During the following six months, the PDI scores for all children continued to improve, although not in a linear fashion. The East Asian children maintained their lead over the Chinese children, while the gap between Russian and Chinese children grew wider. Of note, the PDI scores for all infants in this study were 0.33 SD to 1.67 SD below the mean scores of the BSID-II normative sample.
The Movement Assessment Battery for Children
A standardized tool used to evaluate motor skills in children aged four years and older, the MABC11 evaluates both fine and gross motor skills and was standardized on 1234 American children representative of the general population, including children of different ethnic backgrounds, eg, “white,” “black,” and “other” ethnic origins in approximately the same proportions as existed in the United States in the 1980s.11 Miyahara et al.38 assessed the suitability of the MABC for Japanese children. One hundred thirty-three children, ages seven to 11 years, participated. In the three age bands administered (seven to eight years of age; nine to ten years of age; and 11–12 years of age), 29% of items yielded a significant difference (p < 0.01). When examining the results for each age band separately, a trend became apparent. Older children had more item scores that were significantly different from their American peers than did younger children, with the direction for these differences due mostly to superior American performance. Overall, 45% of 11-year-old children fell below the fifth percentile American norms, leading the authors to suggest that the MABC’s norms might not be appropriate for Japanese children.
Chow and colleagues39 administered the MABC to 255 Hong Kong children ages four to six years. In contrast to Mihayara et al.’s results,38 Chow et al.39 found that Chinese children performed significantly better than their American counterparts on items related to manual dexterity and dynamic balance, while the American children performed better on items relating to projection and reception of moving objects.
When Chow et al.40 incorporated the scores from these 255 children with those of 544 other children aged four and six years from Taiwan and compared them with the American normative sample, both within- and cross-cultural differences were significant when considering all items of the MABC. Effect sizes, however, were too small to be considered meaningful. The authors reported that descriptive analysis of the cut-off scores for identification of delays suggested that certain items would need to be adjusted prior to using this test in a Chinese population.
Wright and colleagues41 investigated the usefulness of the MABC Checklist, a second part of the MABC package, in Singapore by assessing 212 children seven or eight years of age. Findings indicated that although the percentage of children having movement disorders was quite similar to the value obtained in the normative sample, quite a few items needed modification to allow completion in Singapore.
Motor Milestone Attainment Differences
The foregoing studies illustrate motor development differences among children of various ethnic backgrounds with data supporting discrepancies between children of European and Asian backgrounds. Not only did the rate of skill acquisition differ among children of different ethnic origins but limited evidence also suggests that elements in the sequence of skill acquisition may also differ. In one available study, a sample of 72 infants from Hong Kong rolled from supine to prone prior to rolling from prone to supine,42 contrary to the sequence identified in a Canadian normative study.8
Other Factors Affecting Motor Development Rate and Sequence
This literature review illustrates differences in the rate of gross motor development and provides limited evidence of variation in the sequence of rolling attainment among children of different ethnic origins. This review highlights why it may be inappropriate to compare children with an ethnically diverse, representative sample of the general population. Many factors, in addition to ethnic background, have been postulated to affect children’s rate and sequence of gross motor development, such as sex, socioeconomic status, nutrition, early postural experience, and parental expectations.13,19,43 When looking specifically at the literature pertaining to children of Asian and European backgrounds, the authors of the reviewed studies hypothesize that socio-cultural and environmental factors may partially explain differences in motor development. These factors include children of Asian background being less exposed to prone-lying,19,24,25,29–31,42 or being positioned upright,27 the increased incidence of sleeping in a hammock,27 the use of swaddling,29 or differences in clothing which may make it easier or more difficult to move.42
Other factors that are suggested to play a role in influencing motor development include the level of emphasis placed on independence in activities of daily living at an early age,28,29,31 and the degree of importance placed on motor skills such as ball manipulation,39 and bicycle riding.41 It has also been hypothesized that children of Asian background may have less opportunity to try new skills as Asian parents may be protective because of an increased fear of injury,33 while others theorize that children of Asian background have greater opportunity to learn new motor skills as they are given more opportunity to move about once beyond infancy.27 Finally, when looking at differences in motor development in children adopted from Asian countries, Pomerleau and colleagues37 suggested that malnutrition, orphanage conditions, and a lack of experience with play objects could influence motor development.
The Canadian Institute of Child Health44 reported that 7.7% of Canadian children live with a disability. Infant motor development is an important indicator of neurological integrity45 and can be used to identify children at risk for neurodevelopmental delay12 and disability. Although the evidence supporting early intervention effectiveness is conflicting,2–5 the best chance for positively influencing children’s developmental outcome is to identify children with delays as promptly as possible in order to begin intervention.1,6 Although children with significant delays are generally easy to identify early in life, it is more difficult to identify children with milder delays.45 Considering that these may be the children for whom early intervention services have the most benefit, it is crucial that they be identified as early as possible.46
Early identification requires reliable and valid discriminative tools that have been standardized on a normative sample representative of the population. The sample should include the same proportions of children of different ethnic origins as in the general population. By using such a comparison group, however, it is possible that children are being compared with other children’s scores that are not typical of development of those of their ethnic origin and that they are therefore incorrectly identified as advanced, typical or delayed. Although differences in motor development of children may be the result of various factors,13,19,43 the literature reviewed suggests differences in rate of motor development among children of various ethnic origins, including those of Asian and European descent.7,11,20,24,27,29,32,36,38–40 Limited support suggests also that certain developmental milestones, such as rolling,42 may differ between infants of Asian and European origin.
Considering the number of standardized, discriminative motor tools in existence, it was puzzling that only four tools were represented in the reviewed literature. More than half of these articles were published more than 10 years ago, and most relate to the original DDST, an outdated tool. This speaks to the lack of available research on the appropriateness of normative data for currently used, discriminative motor assessments.
Therefore, caution is advised when interpreting results from discriminative motor assessment tools with children of different ethnic backgrounds until there is enough evidence surrounding the motor development of children of various backgrounds living within one country. Further examination of similarities and differences in neuromotor development among children of different ethnic groups living within each country is needed to help facilitate identification of children with delays and ensure that they are being compared to an appropriate normative sample. This, in turn, will help provide children and their families with the support they deserve to achieve a complete state of physical, mental, and social well-being, leading to full participation in society47 or, more simply put, health.
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© 2007 Lippincott Williams & Wilkins, Inc.